package com.example.kaoshi;

import java.util.Scanner;

/**
 * Created by Quincy on 2018/10/11.
 */
public class KaPian {

    public static void main(String[] args){
        Scanner scanner = new Scanner(System.in);
        float len = scanner.nextFloat();

        System.out.println(number_of_cards(len));
    }

    private static int number_of_cards(float length){
        int n = 1;
        double sum = 0.0;
        while (true){
            sum +=(double) 1/(n+1);
            if (sum < length)
                n++;
            else
                break;
        }
        return n;
    }
}
